Formation of W/HfO$_2$/Si gate structures using in situ magnetron sputtering and rapid thermal annealing

The W(150 nm)/HfO$_2$(5 nm)/Si(100) structures prepared in a single vacuum cycle by rf magnetron sputtering were subjected to rapid thermal annealing in argon. It is found that at an annealing temperature of 950$^\circ$C, the tungsten oxide WO$_x$ phase and the hafnium silicate HfSi$_x$O$_y$ phase grow at the W/HfO$_2$ and HfO$_2$/Si(100) interfaces, respectively. Herewith, the total thickness of the oxide layeris 30% larger than that of the initial HfO$_2$ film. In addition, a decrease in the specific capacitance in accumulation C$_{\mathrm{max}}$ and in the dielectric constant k (from 27 to 23) is observed. At an annealing temperature of 980$^\circ$C, intensive interaction between tungsten and HfO$_2$ takes place, causing the formation of a compositionally inhomogeneous Hf$_x$Si$_y$W$_z$O oxide layer and further decrease in C$_{\mathrm{max}}$. It is shown that a considerable reduction in the leakage currents occurs in the W/HfO$_2$/X/Si(100) structures, where X is a nitride barrier layer.